Abstract

The majority of species in ecosystems are rare, but the ecosystem consequences of losing rare species are poorly known. To understand how rare species may influence ecosystem functioning, this study quantifies the contribution of species based on their relative level of rarity to community functional diversity using a trait-based approach. Given that rarity can be defined in several different ways, we use four different definitions of rarity: abundance (mean and maximum), geographic range, and habitat specificity. We find that rarer species contribute to functional diversity when rarity is defined by maximum abundance, geographic range, and habitat specificity. However, rarer species are functionally redundant when rarity is defined by mean abundance. Furthermore, when using abundance-weighted analyses, we find that rare species typically contribute significantly less to functional diversity than common species due to their low abundances. These results suggest that rare species have the potential to play an important role in ecosystem functioning, either by offering novel contributions to functional diversity or via functional redundancy depending on how rare species are defined. Yet, these contributions are likely to be greatest if the abundance of rare species increases due to environmental change. We argue that given the paucity of data on rare species, understanding the contribution of rare species to community functional diversity is an important first step to understanding the potential role of rare species in ecosystem functioning.

Ancillary

Article Information

DOI

Format Available

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Figure S2. Pearson's correlation coefficients (r) between the four traits considered in our study: leaf nitrogen, leaf mass per area (LMA), root-to-shoot ratio, and plant mass.

Figure S3. Summary of principal component analysis of the four selected traits across the 46 species.

Figure S4. Principal component-based convex hull volumes, showing the influence of individual species on the change in hull volume.

Figure S5. Contribution of each species to abundance-weighted community functional trait volume based on the four measures of rarity used in this study.

Figure S6. Comparison of the contribution of each of the 46 species to functional trait volume compared with the contribution of the same species to 1111 constructed null communities.

Please note: Wiley-Blackwell is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.